Both boiling water and pressurized water nuclear reactor plants employ various valves that must perform reliably in the operating reactor environment. In the case of a boiling water plant, a typical environment includes 540.degree. F. water at 1000 psi with varying oxygen concentrations up to saturation conditions. In a pressurized water plant, on the primary side, water temperatures of approximately 600.degree. F. at approximately 2200 psi are commonly found, with the secondary side being at approximately 540.degree. F. and 1000 psi.
Among the valves that must operate in these environments are normally closed, pilot-operated safety/relief valves. The pilot stage assembly of such a valve includes a pilot valve that has mating seating surfaces that are continuously urged together under considerable force for extended periods of time. A serious problem facing the industry is that these mating seating surfaces tend to become bonded together over time in the reactor environment, resulting in valve malfunction particularly with respect to such valves not opening at their set points.